Republican efforts to replace the Affordable Care Act collapsed in the Senate on Monday evening as two more GOP senators announced they would oppose the latest plan backed by their party’s leadership.

The announcements by Sens. Mike Lee of Utah and Jerry Moran of Kansas brought to four the number of Republican senators opposed to even bringing the bill to the Senate floor for debate. With all Senate Democrats opposed, the “no” votes were enough to kill the measure.

It had long been unclear whether Senate Majority Leader Mitch McConnell would be able to marshal the 50 votes needed from his 52-seat majority. But the abrupt failure of the GOP measure marked another embarrassing defeat in the years-long effort by Republicans to repeal the health care law, also known as Obamacare.

With the failure of the repeal-and-replace legislation, McConnell said late Monday that he will instead try to hold a vote in the coming days on a repeal-only bill, with a two-year delay to give Congress time to pass a replacement health care law.

Prospects for such a bill remain unclear because it could leave millions of Americans without coverage and wreak havoc on the insurance industry.

In a tweet Monday, President Donald Trump voiced support for repeal only: “Republicans should just REPEAL failing ObamaCare now & work on a new Healthcare Plan that will start from a clean slate. Dems will join in!”

Conservative senators complained that the bill McConnell put forward last week, the Better Care Reconciliation Act, did not go far enough in gutting Obamacare, and centrists were worried about its steep cuts to Medicaid, the health insurance program for the poor.

Before Monday’s defections, two Republicans, Susan Collins of Maine and Rand Paul of Kentucky, had already said they would vote against the legislation.

“We should not put our stamp of approval on bad policy,” Moran said in a statement Monday. “We must now start fresh.”

Lee wanted tougher rollbacks of Obamacare mandates and said he opposed the bill because it would not lower costs for healthy Americans whose insurance premiums were pushed up by the need to subsidize costs for those who were ill.

“In addition to not repealing all of the Obamacare taxes, it doesn’t go far enough in lowering premiums for middle class families; nor does it create enough free space from the most costly Obamacare regulations,” Lee said in a statement.

The sudden announcement from Lee, a leading conservative, and Moran, who headed the Senate Republican campaign committee in the 2014 election, came as Trump was dining at the White House with several GOP supporters of the bill. That timing made their announcements a more stinging rebuke of the White House’s efforts on behalf of the measure.

Trump had just begun ramping up his efforts to lobby GOP senators. After being largely absent from the legislative process in recent weeks, the president called wayward Republican senators over the weekend, including Lee.

Though McConnell could have attempted to put together a new version of the legislation, senators made clear their concerns would not be easily addressed.

Beyond the four announced opponents, several other Republican senators had strong doubts about the bill. Earlier in the day, Sen. Ron Johnson of Wisconsin, one of the Senate’s most conservative members, had said he might oppose the bill.

Johnson said he objected to statements McConnell had made in efforts to reassure centrist senators. According to Johnson, McConnell had told those senators that the steep Medicaid cuts wouldn’t take effect for years and might never happen.

On the other side of the debate, Collins and other centrists pointed to Congressional Budget Office estimates that that GOP plan would leave 22 million more Americans without health insurance by 2026. She too voiced serious doubts about whether the current version could be adequately revised.

The Republican bill also faced mounting opposition from the health insurance industry. Insurers until recently had resisted public criticism of the GOP health care campaign. On Friday, however, they issued a blistering critique of the latest version of the Senate legislation.

The industry’s two leading trade groups called the bill “unworkable” and warned that it would make it more difficult for sicker Americans to get coverage, echoing warnings from the nonpartisan CBO, the American Academy of Actuaries and others.

As the bill’s fate appeared increasingly in doubt, Republican lawmakers have been under intense pressure not to be the senator whose vote was the final one to kill the bill. By making their announcement together, Moran and Lee may have hoped to avoid that label.

The move also exposed a new rupture among conservatives. An amendment from Sen. Ted Cruz, R-Texas, to allow insurers to offer low-priced, bare-bones plans was supposed to draw conservative support.

But it was not enough for Lee, a longtime Cruz friend and ally, or Paul, who was among the first senators to reject the Senate bill.

Democrats welcomed the latest setback as they push Republicans to end their efforts to repeal Obamacare and instead work together to fix it.

“This second failure of Trumpcare is proof positive that the core of this bill is unworkable,” said Sen. Charles E. Schumer, D-N.Y., referring to the original Senate bill, which had to be revised to address lawmakers’ concerns. “Rather than repeating the same failed, partisan process yet again, Republicans should start from scratch and work with Democrats on a bill that lowers premiums, provides long-term stability to the markets and improves our health care system.”

Sen. John McCain, who has also expressed concerns about the bill, endorsed a more collaborative approach to drafting legislation.

“Congress must now return to regular order, hold hearings, receive input from members of both parties and heed the recommendations of our nation’s governors,” he said in a statement from Arizona, where he is recovering from surgery to remove a blood clot from above his eye.

McConnell had said publicly that if the bill failed, he might do exactly that, turning to Democrats to help stabilize the current law. But many viewed that as more of a threat designed to pressure GOP members to fall in line.

Despite the latest setbacks, efforts to revise the Senate bill could yet continue. House Republicans similarly failed in several attempts before finally passing their version in spring. But the White House has been unable, or unwilling, to exert similar pressure on Republican senators that it did on House members, and time is narrowing on the legislative calendar to accomplish other GOP goals.

The Trump administration has also been distracted by the growing investigation into Russia’s meddling in the 2016 election and by the president’s sagging popularity.